ENH: template indicators with jinja

setup.py

@@ -47,6 +47,7 @@
     "scipy>=1.2",
     "statsmodels",
     "xarray>=0.17",
+    "Jinja2",
 ]
 
 dev_requirements = []

xclim/core/formatting.py

@@ -14,8 +14,10 @@
 from inspect import _empty, signature  # noqa
 from typing import Any, Mapping, Sequence
 
+import numpy as np
 import xarray as xr
 from boltons.funcutils import wraps
+from jinja2 import Environment
 
 from xclim.core.utils import InputKind, PercentileDataArray
 
@@ -34,6 +36,8 @@
     "pr_per_period": "{unkown}",
 }
 
+jinja_env = Environment()
+
 
 class AttrFormatter(string.Formatter):
     """A formatter for frequently used attribute values.
@@ -77,7 +81,8 @@ def format(self, format_string: str, /, *args: Any, **kwargs: dict) -> str:
         for k, v in DEFAULT_FORMAT_PARAMS.items():
             if k not in kwargs:
                 kwargs.update({k: v})
-        return super().format(format_string, *args, **kwargs)
+        kwargs["np"] = np  # noqa
+        return jinja_env.from_string(format_string, globals=kwargs).render()
 
     def format_field(self, value, format_spec):
         """Format a value given a formatting spec.